Triple‐Functional Hydrazide‐Based Modifier for Self‐Assembled Monolayers/Perovskite to Obtain 26.29%‐Efficiency Inverted MA‐Free Perovskite Solar Cells

Inverted perovskite solar cells (PSCs) face challenges in hole-transport layer (HTL) uniformity and buried interface defect passivation. To address these issues, we introduce 4-(methylthio)benzhydrazide (MTBH) as a triple-functional modifier for self-assembled monolayers (SAMs)/perovskite to enhance the performance of inverted PSCs. MTBH simultaneously optimizes the [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) SAMs and passivates perovskite defects through ternary synergistic interactions: (1) P═O→S-C coordination between Me-4PACz and MTBH improves SAMs ordering and energy-level alignment; (2) N─H⋯I^- hydrogen bonding passivates iodine vacancies; (3) C═O→Pb²⁺ coordination repairs undercoordinated lead defects. These interactions regulate perovskite crystallization kinetics, inducing a "fast nucleation-slow growth" mode that yields high-quality films with reduced residual stress (18.0 MPa versus Control's 60.1 MPa) and suppressed grain-boundary defects. Consequently, MTBH-incorporated devices achieve a champion power conversion efficiency (PCE) of 26.29% (versus 23.62% for control) with a high fill factor (FF: 84.94%) and open-circuit voltage (V_OC: 1.19 V). The devices also exhibit exceptional stability, retaining 93.76% PCE after 2000 h in ambient air and 98.0% after 470 h of maximum power point tracking.